Just as an oil lamp burns in dependence on oil & wick...

"Sensing a feeling of pleasure, he discerns that it is inconstant, not grasped at, not relished. Sensing a feeling of pain... Sensing a feeling of neither-pleasure-nor-pain, he discerns that it is inconstant, not grasped at, not relished. Sensing a feeling of pleasure, he senses it disjoined from it. Sensing a feeling of pain... Sensing a feeling of neither-pleasure-nor-pain, he senses it disjoined from it. When sensing a feeling limited to the body, he discerns that 'I am sensing a feeling limited to the body.' When sensing a feeling limited to life, he discerns that 'I am sensing a feeling limited to life.' He discerns that 'With the break-up of the body, after the termination of life, all that is sensed, not being relished, will grow cold right here.'

"Just as an oil lamp burns in dependence on oil & wick; and from the termination of the oil & wick — and from not being provided any other sustenance — it goes out unnourished; in the same way, when sensing a feeling limited to the body, he discerns that 'I am sensing a feeling limited to the body.' When sensing a feeling limited to life, he discerns that 'I am sensing a feeling limited to life.' He discerns that 'With the break-up of the body, after the termination of life, all that is sensed, not being relished, will grow cold right here.'"

Gelañña Sutta

The Sick Ward (1)

http://www.accesstoinsight.org/tipitaka/sn/sn36/sn36.007.than.html#oil